Heat exchanger assembly

ABSTRACT

A heat exchanger, includes a plurality of MCC microchannel tubes, each microchannel tube of the plurality of microchannel tubes having at least one microchannel fluid passage defined therein and having a chord, the chord being the orthogonal distance from a leading edge to a trailing edge, each microchannel tube of the plurality of microchannel tubes being disposed such that the chord is less than orthogonally disposed relative to a heat exchanger plane. A method of forming such a heat exchanger is further included.

FIELD OF THE INVENTION

This invention relates generally to cooling systems, and moreparticularly to heat exchangers usable in such cooling systems.

BACKGROUND OF THE INVENTION

Typical refrigeration systems often utilize conventional fin-and-tubeheat exchanger coils to dissipate heat from refrigerant passing throughthe heat exchanger coils. Usually, in large-scale cooling systems, asingle, oftentimes large, conventional fin-and-tube heat exchanger coil100, as depicted in prior art FIG. 3, is sized to dissipate or reject anamount of heat equal to the heat load of the refrigeration system.Multiple conventional fin-and-tube heat exchanger coils 100 might alsobe used. The fin-and-tube heat exchanger coil(s) is/are sized todissipate the amount of heat in the refrigerant that was absorbed inother portions of the refrigeration system.

Usually, in large-scale cooling systems, the fin-and-tube heat exchangercoil(s) is/are positioned outside a commercial building, such as on arooftop, to allow heat transfer between the fin-and-tube heat exchangercoil and the outside environment (i.e., to allow the heat in therefrigerant to dissipate into the outside environment). Further, naturalor ram airflow may be augmented by a mechanical airflow that may beprovided by a fan, for example, to assist in air-cooling thefin-and-tube heat exchanger coil.

Fin-and-tube heat exchanger coils, depicted generally at 100, in priorart FIG. 3, often display less than ideal efficiencies and relativelyhigh cost in dissipating heat from the refrigerant passing through thecoils as compared to newer technologies. Typically, fin-and-tube heatexchanger coils can be rather large for the amount of heat they candissipate from the refrigerant as compared to newer technologies.Additionally, fin-and-tube heat exchanger coils use a great deal ofcopper in their construction. Presently, copper is a very expensivecommodity. Further, the larger the heat exchanger coil becomes, the morerefrigerant used in the refrigeration system, thus effectivelyincreasing the risk of potential damage to the environment by anaccidental atmospheric release. The efficiency of fin-and-tube heatexchanger coils is however not very dependent on the direction of theair flow relative to the coils the coils. This can be seen in prior artFIG. 3, the arrows indicating air flow over the various tubes 102.

A more recent form of heat exchanger is the microchannel coil (MCC) heatexchanger. Microchannel coil (MCC) heat exchangers are typically made ofaluminum, replacing the costlier copper of the fin-and-tube heatexchanger coils. Further, in similar heat exchange applications, MCCheat exchangers can be made significantly smaller than fin-and-tube heatexchanger coils that effect similar heat exchanges. To date, however,microchannel coil (MCC) heat exchangers are known to be quite sensitiveto the direction of airflow relative to the plane of the MCC heatexchanger. Efficiency drops off dramatically as the direction of airflowvaries from the normal relative to the plane of the MCC heat exchanger.

Currently, the major application of microchannel coils is in theautomotive industry. Microchannel coils 110 may be used as a condenserand/or an evaporator in the air conditioning system of an automobile.See prior art FIGS. 1 and 2. A microchannel heat exchanger coil, forexample, in an automotive air conditioning system, is typically locatedtoward the front of the engine compartment, where space to mount theheat exchanger coil is limited and where the direction of airflow isnormal. Therefore, the microchannel heat exchanger coil, which is muchsmaller, lighter, and less costly than a conventional fin-and-tube heatexchanger coil that would otherwise be used in the automotive airconditioning system, is a suitable fit for use in an automobile.

Referring to FIGS. 2 and 7, the prior art MCC tube heat exchanger 110includes an inlet header 116 and a spaced apart outlet header 118. Eachof the headers 116, 118 has a fluid passageway 121 defied therein. Therespective fluid passageways 121 are in fluid communication by means ofthe microchannel tubes 112 that extend between the headers 116,118. Theheaders 116,118 each have a known depth dimension 119. A heat exchangerplane 125 includes the longitudinal axes 126 of the headers 116, 118 andcan be thought of as the windward face of the MCC tube heat exchanger110. The plane 125 is usually presented normal to the incoming air flow.

The MCC tube heat exchanger 110 includes a plurality of microchanneltubes 112. Each microchannel tube 112 has a length dimension 114extending from header 116 to header 118, as depicted in prior art FIG.7. The two edges 120, 122 are joined by two spaced apart, parallelrelatively long sides 124 defining a chord 123 of the microchannel tube112. In cross section, the edges 120, 122 and sides 124 of themicrochannel tube 112 define a very thin rectangle with an interiorfluid passage 113. The fluid coupling of the headers 116, 118 is bymeans of the plurality of microchannel tubes 112. In the prior art MCCtube heat exchanger 110, the chord 123 of each of the microchannel tubes112 is disposed orthogonally with respect to the plane 125 of the MCCtube heat exchanger and the length of the chord 123 is therefore limitedto a maximum equal to the depth 119 of the respective headers 116, 118.

The prior art MCC tube heat exchanger 110 further includes fins 130, asdepicted in prior art FIGS. 8 and 9. The fins 130 are typically formedof a single metallic ribbon that is compressed at series of bends 131,the bends 131 being formed in alternating directions. The ribbon of thefins 130 is affixed at the alternating bends 131 to respective adjacentmicrochannel tubes 112 in a heat conducting joint. The fins 130 includeheat exchange surfaces 132. The plane of each of the heat exchangesurfaces 132 is, in the prior art, usually disposed generally orthogonalwith respect to a respective side 124 of an adjacent microchannel tube112, adjacent heat exchange surfaces 132 being disposed in a parallelarray. The height dimension 134 of the heat exchange surfaces 132 isabsolutely limited by the distance 134 between adjacent microchanneltubes 112.

The plane of adjacent fins 130 of some prior art MCC heat exchangers 110is angled with respect to one another. The ribbon forming the fins 130has very sharp bends. See U.S. Pat. No. 6,988,538. Such alternateangling reduces the number of heat transferring heat exchange surfaces132 that can be included in a given length 114 of the microchannel tube112 and the sharp bends 131 provide for only a minimal heat conductingjoint with the respective microchannel tube 112. For these reasons thealternating angling disposition is not favored as being less efficientthan the parallel array disposition of prior art FIGS. 8 and 9.

For most efficient heat exchange in the prior art, the flow of airthrough the MCC tube heat exchanger 110 is normal to the plane 125 ofthe heat exchanger 110, as depicted in prior art FIGS. 1 and 2.Efficiency of the known MCC tube heat exchanger 110 depends on the flowof air being substantially parallel with the chord 123 and across thetwo sides 124, as depicted in prior art FIG. 2, and past theorthogonally disposed fins 130. For this reason, the most efficient ofall known uses of the MCC technology has been with normal air flowrelative to the plane of the MCC heat exchanger, where the leading edge120 of each microchannel tube 112 is presented to the air flow and theair flow proceeds down both sides 124 to the trailing edge 122.

Angling the known MCC tube heat exchanger 110 to the direction ofairflow results in known and calculable reductions of efficiency, ascompared to normal airflow with the same MCC tube heat exchanger 110.Such angling is noted in Prior art FIGS. 4-6. Angling of the MCC tubeheat exchanger 110 reduces the footprint of the heat exchanger unit,which in turn reduces cost. However, such angling disadvantageouslysacrifices efficiency of the heat exchanger unit because the MCC tubeheat exchanger 110 is angled with respect to the fan 140 and airflowthrough the MCC tube heat exchanger 110 is then not normal, but isturned. A resulting issue with heat exchanger units that are mounted ona rooftop is that the airflow is typically turned 90 degrees as it flowsthrough the heat exchanger. This results from a horizontally mounted fan140 drawing in a generally horizontal flow of air 142 and expelling theairflow 142 in a generally vertical direction. Such flow path changeresults in reduced efficiency of the MCC tube heat exchanger 110. Forexample a representative reference local loss coefficient of theorientation depicted in prior art FIG. 4 is 0.83. The coefficient isdirectly applied to a local mass flow, resulting in a significantlydiminished mass flow.

The above reduction of mass flow has led engineers to angle known MCCheat exchangers 110 to the relative airflow, such as the 60 degree angleof prior art FIGS. 5 and 6 in which the direction of air flow 130 is notnormal to the plane 125 of the MCC tube heat exchanger 110. Such anglingadvantageously results in a greater height dimension of the MCC heatexchangers 110 relative to the overall height of the heat exchangerunit. Further, angling the MCC heat exchangers 110 results in a reducedfootprint of the heat exchanger unit, thereby reducing cost. While costis reduced, efficiency is reduced as a result of the MCC heat exchangers110 being angled with respect to the fan 140. In this case, theexemplary reference local loss coefficient of the angled orientation is0.38, a considerable reduction as compared to the orientation of FIG. 4,but still a significant source of energy loss. Even this reduced lossgenerates a significant loss in airflow velocity and loss in efficiencyof the MCC tube heat exchanger 110.

There is a need in the industry for more efficient MCC tube heatexchangers in applications in which the flow of air is not normal to theplane of the heat exchanger. In this situation, the direction of airflowis altered from the intake side of the MCC tube heat exchanger to theexhaust side by as much as ninety degrees. As noted above, with knownMCC tube heat exchangers, such non-normal air flow significantlydiminishes the efficiency of the MCC tube heat exchanger as compared tonormal air flow on both the intake and exhaust sides of the MCC tubeheat exchanger.

SUMMARY OF THE INVENTION

The present invention substantially meets the aforementioned needs ofthe industry by providing a high efficiency MCC tube heat exchanger foruse with air flows that are not normal to the MCC heat exchanger. Thepresent invention provides, in one aspect, a heat exchanger assemblyadapted to efficiently condense a refrigerant in a refrigeration systemwhere the flow of air to the MCC tube heat exchanger is not normal. TheMCC tube heat exchanger assembly includes at least one microchannel heatexchanger coil including an inlet header and an outlet header, eachmicrochannel of the coil being angled with respect to the plane of theMCC heat exchanger.

The present invention provides, in a further aspect, a method ofassembling a MCC tube heat exchanger assembly. The MCC tube heatexchanger assembly may be adapted to condense a refrigerant for use in arefrigeration system. The method includes forming a MCC tube heatexchanger assembly with angled microchannel tubes and/or fins thatprovide for increased efficiency of the MCC tube heat exchanger assemblywhen the MCC tube heat exchanger assembly is angled with respect to thedirection of airflow, i.e. the air flow is not normal to the plane ofthe MCC tube heat exchanger assembly.

The present invention provides, in addition to microchannel tubes andfins oriented to non-normal air flow, a greater heat transfer area ofthe respective microchannels and fins for a given depth of the headersof the MCC heat exchanger. Efficiency of the device of the presentinvention is therefore improved by two means. The first is angling themicrochannel tubes and fins into the airflow and the second is thegreater heat changer area of the microchannel tubes and fins presentedto the air flow that is made possible by the angling of themicrochannels and/or fins.

The present invention is a heat exchanger that includes a plurality ofMCC microchannel tubes, each microchannel tube of the plurality ofmicrochannel tubes having at least one microchannel fluid passagedefined therein and having a chord, the chord being the orthogonaldistance from a leading edge to a trailing edge, each microchannel tubeof the plurality of microchannel tubes being disposed such that thechord is less than orthogonally disposed relative to a heat exchangerplane. The present invention is further a method of forming such a heat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a prior art MCC heat exchanger;

FIG. 2 is a sectioned perspective view of a prior art MCC heatexchanger;

FIG. 3 is a perspective view of a sectioned prior art fin and tube heatexchanger;

FIG. 4 is a partially sectioned perspective view of a prior art MCC tubeheat exchanger;

FIG. 5 is a perspective view of a of a prior art MCC tube heatexchanger;

FIG. 6 is a side elevational schematic of a prior art heat exchangerassembly employing prior art MCC tube heat exchangers;

FIG. 7 is a perspective view of a prior art heat exchanger as employedin the heat exchanger assembly of FIG. 6;

FIG. 8 is an elevational view of the microchannel tubes and fins of theprior art MCC tube heat exchanger of FIG. 7;

FIG. 9 is a perspective view prior art fins of FIG. 8;

FIG. 10 includes three-side elevational schematic depictions of heatexchanger assemblies in v-shape, single heat exchanger, and w-shapeconfigurations;

FIG. 11 is a side elevational schematic of a v-shaped heat exchangerassembly employing two MCC tube heat exchangers of the presentinvention;

FIG. 12 is a perspective view of a MCC tube heat exchanger of thepresent invention as employed in the heat exchanger assembly of FIG. 11;

FIG. 13 is a front elevational depiction of the microchannel tubes andfins of the present invention;

FIG. 14 is a perspective view of the fins of the present invention;

FIG. 15 is a perspective view of a portion of a MCC tube heat exchangerof the present invention employing both angled microchannel tubes andangled fins;

FIG. 15 a is a perspective view of a microchannel tube of the presentinvention having curved sides;

FIG. 15 b is a perspective view of a microchannel tube of the presentinvention having an airfoil shape; and

FIG. 16 is a perspective view of a portion of a MCC tube heat exchangerof the present invention employing both angled microchannels and angledfins.

DETAILED DESCRIPTION OF THE DRAWINGS

The heat exchanger assembly of the present invention is depictedgenerally at 10 in the figures. The heat exchanger assembly 10 may beused as a heat exchanger in a large-scale refrigeration system, such asthat found in many commercial applications and multi-unit residences. Insuch a refrigeration system, the heat exchanger assembly 10 isfrequently positioned outside the building, such as on the rooftop ofthe building, to allow heat transfer from the heat exchanger assembly 10to the outside environment. The coils 14 of the heat exchanger assembly10 may be advantageously disposed in a non-normal relationship relativeto the incoming airflow. The usual role of the heat exchanger assembly10 in the refrigeration system is to receive compressed, gaseousrefrigerant from one or more compressors (not shown), condense thegaseous refrigerant back into its liquid form, and discharge thecompressed, liquid refrigerant to one or more evaporators (not shown)located inside the store. The liquid refrigerant is evaporated when itis passed through the evaporators, and the gaseous refrigerant is drawninto the one or more compressors for reprocessing into the refrigerationsystem.

Refrigerants are typically given an R-XXX designation, such as “R-134a”or “R-22.” Additionally, other compounds, such as anhydrous ammonia, forexample, may be used in such a refrigeration system to providesufficient cooling to the refrigeration system. If any of the R-XXXdesignated refrigerants is used as the refrigerant of choice, thecomponents of the refrigeration system in contact with the R-XXX may bemade from copper, aluminum, or steel, among other materials. However, asunderstood by those skilled in the art, other refrigerants may not becompatible with some materials. If anyhydrous ammonia, for example, isused as the refrigerant of choice, copper components of therefrigeration system in contact with the anyhydrous ammonia may corrode.Alternatively, other refrigerants (including both two-phase andsingle-phase refrigerants or coolants) may be used with the heatexchanger assembly 10.

In addition to large refrigeration systems as noted above, the heatexchanger assembly 10 may also be used in various process industries,where the heat exchanger assembly 10 may be a portion of a fluid coolingsystem using a single-phase coolant (e.g., glycol). In such anapplication, the role of the heat exchanger assembly 10 in the fluidcooling system is to receive heated liquid coolant from one or more heatsources (e.g., a pump or an engine, for example), cool the heatedliquid, and discharge the cooled liquid coolant to one or more heatsources. The cooled liquid coolant is again heated when it is put inthermal contact with the one or more heat sources, and the heatedcoolant is routed by the pump for re-processing into the fluid coolingsystem.

Further, the heat exchanger assembly 10 may be used with vehicles,including in applications using either two-phase or single-phaserefrigerants or coolants. Such applications include, for example, airconditioning systems and the engine cooling system. The application ofthe heat exchanger assembly 10 is particularly desirable in low frontalprofile vehicles where it may be desirable to angle the heat exchangerassembly 10 with respect to the incoming airstream, such angling beingnecessary to achieve sufficient cooling while maintaining a desired lowfrontal profile of the vehicle.

As depicted in FIGS. 10 a and 11, the heat exchanger assembly 10 mayinclude two microchannel heat exchanger coils 14 a, 14 b being supportedby a frame 18. The frame 18 may be a freestanding structure. However,the frame 18 may comprise any number of different designs other thanthat shown. As such, the illustrated frame 18 is intended forillustrative purposes only.

FIGS. 10 a, 10 b, and 10 c depict exemplary embodiments of the heatexchanger assembly 10 of the present invention. Such embodiments aretypical of rooftop installations where the heat exchanger assembly 10 isemployed as a condenser. FIG. 10 a is a V configuration employing twoheat exchanger assemblies 10. FIG. 10 b is configuration employing onlya single heat exchanger assembly 10. FIG. 10 c is W configurationemploying four heat exchanger assemblies 10 and having the fans 15 a, 15b set at an angled disposition as compared to the horizontal dispositionof the fans 15 of FIGS. 10 a, 10 b.

As shown in FIGS. 11 and 12, each microchannel heat exchanger coil 14 a,14 b includes an inlet manifold or header 22 and an outlet manifold orheader 26. The headers 22 and 26 are fluidly connected by a plurality ofmicrochannel tubes 30. One or more baffles (not shown) may be placed inthe manifolds 22, 26 to cause the refrigerant to make multiple passesthrough the microchannel tubes 30 for enhanced cooling of therefrigerant. Each of the headers 22, 26 has a known depth dimension 24.A heat exchanger plane 40 is defined including the longitudinal axes 44of the respective headers 22, 26 and an orthogonal line 46 extendingbetween the respective axes 44.

Each of the microchannel tubes 30 extends between a respective header 22and respective header 26. As depicted in FIG. 12, each microchannel tube30 has a length dimension 32 defining the distance between the twoheaders 22, 26 to which the respective microchannel tube 30 are coupled.Each microchannel tube 30 has a leading edge 34 and a trailing edge 36.A pair of opposed sides 38 extend between leading edge 34 and thetrailing edge 36. The area sides 38 of the microchannel tube 30 comprisethe bulk of the heat transfer of the microchannel tube 30. An interiorfluid passage 31, as depicted in FIG. 16, is defined in each of themicrochannel tubes 30. The fluid passage 31 is in fluid communicationwith the fluid passage 25 of the respective headers 22, 26. Each of themicrochannel tubes 30 further has a height dimension 33 and a chorddimension 32. The height dimension 33 extends between the respectiveouter margins of the two sides 38. The chord 35 extends orthogonallybetween the leading edge 34 and the trailing edge 36 and is onedimension in the determination of the area sides 38. The longer thechord 35, the greater the heat exchange area of the sides 38.Advantageously, the microchannel tubes 30 of the present invention areangled at an angle of less than 90 degrees with respect to the plane 40of the MCC tube heat exchanger 14 as depicted in FIGS. 11, 12, 15 and 16and preferably between 10 and 60 degrees. Such angling increases thelength dimension of the chord 35 as compared to the chord 123 of theprior art. The advantage of this angling where the angle of the incomingairflow is less than normal with respect to the MCC tube heat exchanger14 is twofold and is noted below.

Referring to FIGS. 15, 15 a, 15 b, and 16, the microchannel tubes 30 maybe formed to include a single internal passageway 31 or may be formed toinclude multiple internal passageways, or microchannels 42, that aremuch smaller in size than the internal passageway of the coil in aconventional fin-and-tube heat exchanger coil. The microchannels 42 maybe round in cross section, as depicted in FIG. 15 b, or rectangular, asdepicted in FIG. 16. Other shapes may as well be used, as depicted inFIG. 15 a where the sides 38 are curved. The microchannels 42 allow formore efficient heat transfer between the airflow passing over themicrochannel tubes 30 and the refrigerant carried within themicrochannels 42, as compared to the airflow passing over the coil ofthe conventional fin-and-tube heat exchanger coil.

The microchannel tubes 30 may be separated into about twenty or lessmicrochannels 42, with each microchannel 42 being about 0.5-2.0 mm inheight and about 0.5-2.0 mm in width, compared to a diameter of about9.5 mm (⅜″) to 12.7 mm (½″) for the internal passageway of a coil in aconventional fin-and-tube heat exchanger coil. However, in otherconstructions of the flat microchannel tubes 30, the microchannels 42may be as small as 0.4 mm by 0.4 mm, or as large as 4 mm by 4 mm.

Referring to FIG. 15 a, in cross section, the microchannel tubes 30 maybe curved to further enhance the passage of airflow 16 through themicrochannel heat exchanger coil 14 where the direction of the airflowis changing in the passage. In cross section, the microchannel 30 hascurved sides 38 preferably having the same radius so that the distancebetween the sides 38 is constant across the chord 32. Preferably, theedges 34, 36 are parallel.

Referring to FIG. 15 b, in cross section, the microchannel tubes 30 maybe airfoil shaped to even further enhance the passage of airflow 16through the microchannel heat exchanger coil 14 where the direction ofthe airflow is changing in the passage. In cross section, themicrochannel 30 has curved sides 38 preferably having the differentradii to achieve the traditional air foil shape with a radiused leadingedge 34 and tapering to a juncture of the sides 38 at the trailing edge36. Preferably, the edges 34, 36 are parallel. The chord extends fromthe forwardmost point on the radiused leading edge 34 to the trailingedge 36.

The microchannel tubes 30 may be made from extruded aluminum to enhancethe heat transfer capabilities of the flat tubes 30. In the illustratedconstruction, the flat microchannel tubes 30 are about 22 mm wide.However, in other constructions, the flat microchannel tubes 30 may beas wide as 50 mm, or as narrow as 10 mm. Further, the spacing betweenadjacent flat microchannel tubes 30 may be about 9.5 mm. In otherconstructions, the spacing between adjacent flat microchannel tubes 30may be as much as 20 mm, or as little as 3 mm.

In distinction with respect to the prior art, the microchannel tubes 30of the present invention are disposed at an angle of less than ninetydegrees with respect to the plane 40 of the MCC tube heat exchanger 14,the plane 40 including the longitudinal axes 44 of the headers 22, 26and an orthogonally disposed line 46 extending between axles 44. Themicrochannel tubes 30 are therefore disposed such that chords 32 arealso disposed less than orthogonally with respect to the plane 40.

In distinction to the above prior art microchannel heat exchanger 110,the heat exchanger 10 of the present invention mounted as depicted inFIG. 11 at 60 degrees to the incoming airflow has an estimated losscoefficient that is less than 0.38, but greater than 0.05. This reducedloss coefficient provides for a more efficient heat exchanger assembly10 where the airflow is changing direction as the airflow passes throughthe heat exchanger assembly 10. Further, the heat exchanger 10, bysimply tilting the microchannel tubes 30 at 20 degrees from normal (asin the prior art) increases the area of the sides 38 by 6.4% as a resultof the increased length of the chord 32. Such increased area increasesthe heat transfer ability of the microchannel tubes 30, thereby furthercontributing to increased efficiency of the present invention.

For further efficiency improvement of the present invention, the finstock comprising the fins 50, as depicted in FIGS. 13 and 14 is tiltedbetween 10 degrees and 45 degrees with respect to the respectiveadjacent microchannel tubes 30 between which the fins 50 are disposed.As noted in the background section above and depicted in prior art FIGS.8 & 9, in many known applications of microchannel tube heat exchangers110, including its birthplace, the automotive industry, the fin stockdesigns are generally straight, upright and parallel fin-to-fin. In suchorientation, the plane of the radiator elements 132 is disposedorthogonal with respect to the plane of the sides 124 of the adjacentmicrochannel tubes 112 between which the fin 130 is disposed. In suchdisposition, the area of the radiator elements 132 is limited by thespacing dimension 134 between the adjacent microchannels 112.

The tilted fin stock arrangement of the present invention provides for alarger heat exchange surface 56 within the limited installation spacedefined between adjacent microchannel tubes 30. As depicted in FIGS. 13& 14, for a microchannel spacing 58 that is equal to the microchannelspacing 134 in the prior art, the fins 50 angled at a preferred angleare of 20 degrees with respect to the plane of the side 38 of themicrochannel 30 results in about a 15.6% increase in the surface area ofthe heat exchange surface 56 of the fin 50. Such increase in surfacearea significantly increases the efficiency of the tilted fins 50 withrespect to the fins 130 of the prior art.

A further benefit of the tilted fins 50 of the present invention is thatthe bends 54 and the ribbon 52 comprising the fins 50 are formed of aflat section 60 formed between two smaller radius bends 62. The fullarea of the flat section 60 may be joined in a heat conductive joint tothe sides 38 of the adjacent microchannel tubes 30. Such joint has asignificantly greater area as compared to the joint defined between thebin 131 and the side 124 of the microchannel 112 in the prior art. Alarger heat conducting joint results in greater transfer of heat fromthe microchannel 30 to the fin 50.

A depiction of FIGS. 15 & 16 shows both tilted microchannel tubes 30 andtilted fins 50. A user of a heat exchanger 10 as depicted in FIGS. 15 &16 could expect a thermal performance improvement as follows:

Aerodynamic performance improved by 10-20%

Fin stock surface increased by 15.6%

Tube surface increased by 6.4%.

The total estimation of thermal improvement from both the tilted tubeinstallation and the tilted fin stock installation is estimated to begreater than 12%.

The heat exchanger assemblies are described and shown for exemplaryreasons only, and are not meant to limit the spirit and/or scope of thepresent invention.

1. A heat exchanger, comprising: a plurality of MCC microchannel tubes,each microchannel tube of the plurality of microchannel tubes having atleast one microchannel fluid passage defined therein and having a chord,the chord being the orthogonal distance from a leading edge to atrailing edge, each microchannel tube of the plurality of microchanneltubes being disposed such that the chord is less than orthogonallydisposed relative to a heat exchanger plane.
 2. The heat exchanger ofclaim 1, the chord of each microchannel tube of the plurality ofmicrochannel tubes being disposed at an angle relative to the heatexchanger plane that is between ten and sixty degrees.
 3. The heatexchanger of claim 1, the angled disposition of the chord resulting inan increased length of the chord, the increased length dimension of thechord providing for improved thermal performance by means of theresulting greater heat exchange surface area of a respectivemicrochannel tube.
 4. The heat exchanger of claim 1, providing forimproved thermal performance by means of an increased surface area ofeach microchannel tube resulting from the angled disposition thatresults from the chord being less than orthogonally disposed relative tothe heat exchanger plane.
 5. The heat exchanger of claim 1, including aplurality of fins extending between adjacent microchannel tubes, thefins having heat exchange surfaces, the heat exchange surfaces beingless than orthogonally disposed with respect to the sides of therespective adjacent microchannel tubes.
 6. The heat exchanger of claim5, the heat exchange surfaces of the fins being disposed at an anglerelative to the heat exchanger plane that is less than a right angle andgreater than forty-five degrees.
 7. The heat exchanger of claim 5,providing for improved thermal performance by means of the angleddisposition resulting of the heat exchange surfaces of the fins beingless than orthogonally disposed relative to the heat exchanger plane,thereby resulting in a greater heat exchange surface of the fins.
 8. Theheat exchanger of claim 5, providing for improved thermal performance bymeans of an increased surface area of the fin heat exchange surfaceresulting from the angled disposition that results from the heatexchange surface of the fins being less than orthogonally disposedrelative to the heat exchanger plane resulting in a greater microchannelsurface area as compared to an orthogonally disposed radiator elementsof the fins.
 9. The heat exchanger of claim 1, each of the plurality ofmicrochannel tubes being formed with curved sides.
 10. The heatexchanger of claim 1, each of the plurality of microchannel tubes beingformed in an airfoil shape.
 11. A heat exchanger, comprising: aplurality of microchannel tubes; and a plurality of fins disposedbetween adjacent microchannel tubes, the fins having heat exchangesurfaces, the heat exchange surfaces being less than orthogonallydisposed with respect to a side of an adjacent microchannel tube. 12.The heat exchanger of claim 11, the heat exchange surfaces of the finsbeing disposed at an angle relative to the heat exchanger plane that isless than a right angle and greater than forty-five degrees.
 13. Theheat exchanger of claim 11, providing for improved thermal performanceby means of the angled disposition resulting of the heat exchangesurfaces of the fins being less than orthogonally disposed relative tothe heat exchanger plane, thereby resulting in a greater heat exchangesurface of the fins.
 14. The heat exchanger of claim 11, providing forimproved thermal performance by means of an increased surface area ofthe fin heat exchange surface resulting from the angled disposition thatresults from the heat exchange surface of the fins being less thanorthogonally disposed relative to the heat exchanger plane resulting ina greater microchannel surface area as compared to an orthogonallydisposed radiator elements of the fins.
 15. A method of forming a heatexchanger, comprising: forming a plurality of microchannel tubes,defining at least one microchannel fluid passage in each microchanneltube of the plurality of microchannel tubes; providing a microchanneldimension being a chord, the chord being the orthogonal distance from aleading edge to a trailing edge; and disposing each microchannel tube ofthe plurality of microchannel tubes such that the chord is less thanorthogonally disposed relative to a heat exchanger plane.
 16. The methodof claim 15, including forming each of the plurality of microchanneltubes with curved sides.
 17. The heat exchanger of claim 15, includingforming each of the plurality of microchannel tubes in an airfoil shape.18. The method of claim 15, including providing for improved thermalperformance by means of the angled disposition resulting from the chordbeing less than orthogonally disposed relative to the heat exchangerplane resulting in a greater microchannel surface area as compared to anorthogonally disposed microchannel.
 19. The method of claim 15,including extending a plurality of fins between adjacent microchanneltubes, the fins having heat transfer surfaces, and disposing the heattransfer surfaces less than orthogonally with respect to a side of arespective adjacent microchannel tube.
 20. The method of claim 17,including disposing the heat transfer surfaces of the fins at an anglerelative to the heat exchanger plane that is less than a right angle andgreater than forty-five degrees.